1. Field of the Invention
The present invention relates to a broadband antenna, and more particularly, to a broadband antenna which comprises an inductor for increasing the antenna bandwidth, adjusting the impedance matching, and reducing the antenna dimensions.
2. Description of the Prior Art
Electronic products with wireless communication functionalities, such as laptops, tablet PCs, personal digital assistants (PDAs), mobile phones, wireless base stations, smart meters, and USB dongles, utilize antennas to send and receive wireless signals so as to access wireless networks. With the rise of the Long Term Evolution (LTE) technology, there has been a significant increase in demand for broadband antennas, as broadband antennas may improve the transmission rate of wireless communication products. On the other hand, it is also required that the antenna size should be as small as possible in order to meet demand for smaller and lighter products.
The common broadband planar antennas used for LTE systems are planar inverted-F antennas and coupled type antennas. A planar inverted-F antenna has conductive pins which can assist with impedance matching; however, this kind of antenna generally occupies larger space for achieving broadband and high radiation efficiency. A coupled type antenna is generally smaller in size, but its performance can be vulnerable to environment fluctuations and it is hard to design for good impedance matching.
In addition, antennas need to conform to the regulations for Specific Absorption Rate (SAR). Therefore, the antennas used by mobile devices such as tablet PCs, laptops, and mobile phones are usually non-stereo type. However, it is quite challenging to design a non-stereo type antenna with good radiation efficiency. Since reducing external interference to the wireless communication device (i.e. reducing the SAR value) usually comes with the side effect of an impact on radiation efficiency, it is not easy to design an antenna with good radiation efficiency while the antenna also passes the qualification on its SAR.
Therefore, how to increase the bandwidth and efficiency of the antenna that conforms to the SAR regulation while minimizing the antenna size is an important topic that needs to be addressed and discussed.